Metal covered targets are typically used in high energy physics applications. For examples, such targets may be shot with a laser in order to generate plasmas or high energy radiation. Such targets may be used in applications such as inertial confinement fusion.
Targets for lasers used to produce plasma and radiation typically have disadvantages. For example, conventional targets are often produced by micro-machining processes that typically produce targets having a tip sharpness, or apex dimensions, of 25 μm or larger. For example, a current process involves micro-machining a mandrel, electroplating the mandrel with a desired metal, and then etching away the mandrel. Other processes involve depositing a metal layer on a plastic mold and then melting away the plastic mold. The tips of targets produced by such processes can be significantly larger than the wavelength of the laser light that will be used with the target and therefore may not produce optimal energy. Similarly, the apexes, or tips, of the targets can be larger than the focal size (or spot size) of the laser, which can minimize any enhancements that might otherwise be conferred by the target shape.
In addition, such targets are typically manufactured individually and thus can be comparatively expensive. The expense of the targets may limit the number of targets available for use, thus potentially limiting how the targets can be used. For example, a limited number of targets available for a series of experiments may limit the quality or quantity of data obtained during the experiments.
The amount of material available on such targets or irregularities in the target surface may interfere with full characterization of the produced plasma. Insufficient target material may also interfere with optimal energy production.
Some prior experiments have used metal coated silicon targets. However, the silicon included in such targets typically interferes with energy focusing and radiation enhancement.
While hemispherical laser targets have been tested, such targets typically suffer from disadvantages in addition to those noted above. For example, irregularities in the surface of the target, or variations in the targets resulting from their method of manufacture, may make it difficult to properly position the target and position other objects with respect to the target.